Some useful Linux commands

 

  • cat

    cat [file]

    • cat = dump file contents to terminal; ls -l to ensure small file
  • df

    df -h

    • df = show disks space per partition
      • / = separate volume/disk for root os, logs
      • /data = separate volume/disk for websites, apps
    • -h = human readable size
  • grep

    grep [search] [files]

    • grep = filter results, look for patterns in files
    • Example: grep Error *.log
  • htop

    htop

    • htop = top list of processes, nicely colored; can sort, filter
  • kill

    kill [pid]

    • kill = force stop/kill a process; only use for 'hung' process
    • [pid] = pid from ps aux list
  • ls

    ls -lhtr [dir]

    • ls = list contents of directory
    • -l = details
    • -h = human readable sizes
    • -t = sort by time
    • -r = reverse sort, so new shows at bottom
    • -1 = just list names in a single column
    • Example: ls -lhtr logs/*
  • ps

    ps aux

    • ps = process list
    • a = all, including other users
    • u = user format
    • x = register format
    • Example: ps aux | grep nginx
  • reboot

    sudo reboot

    • reboot = reboot server; should not be needed; restart individual services
  • systemctl

    sudo systemctl [action] [process]

    • systemctl = manage services such as nginx, php-fpm
    • Example: sudo systemctl status nginx
    • Example: sudo systemctl restart nginx
    • Example: sudo systemctl status php-fpm
    • Example: sudo systemctl restart php-fpm
  • tail

    tail -f -n50 [file]

    • tail = returns the last few lines of a file
    • -n# = number of lines
    • -f = follow, useful for tailing an active log file
    • Example: tail -f logs/app.log
  • vim

    vim [file]

    • vim, vi = text editor; ls -l to ensure small file
    • arrow keys = move cursor
    • shift G = go to end of file
    • ctrl u = page up
    • ctrl d = page down
    • /[patttern] = search for pattern
    • esc = get out of most vi modes
    • :q = quit
    • :q! = quit without writing
    • :wq = write, quite
    • note, if quit a SSH session with a file vi-ed/open, be sure to SSH in again and cleanup the vi auto backup [file]~; vi-ing the original file again will prompt you about
    • Example: sudo vim /var/log/messages

-End of Document-
Thanks for reading